| Message ID | 20240612021722.239841009@goodmis.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v5,01/13] ring-buffer: Allow mapped field to be set without mapping | expand |
On Tue, 11 Jun 2024 22:16:43 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > In preparation for having the ring buffer mapped to a dedicated location, > which will have the same restrictions as user space memory mapped buffers, > allow it to use the "mapped" field of the ring_buffer_per_cpu structure > without having the user space meta page mapping. > > When this starts using the mapped field, it will need to handle adding a > user space mapping (and removing it) from a ring buffer that is using a > dedicated memory range. > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/ring_buffer.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 28853966aa9a..aa8eb878e0d4 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -491,6 +491,7 @@ struct ring_buffer_per_cpu { > unsigned long pages_removed; > > unsigned int mapped; > + unsigned int user_mapped; /* first user space mapping */ This actually needs to be a counter and not just save the mapped value when it first gets set :-p As the mappings could technically be incremented and decremented differently. I'll send a new patch. But since my long test keeps failing for subtle things, I'm not going to post another series until the full test passes. -- Steve > struct mutex mapping_lock; > unsigned long *subbuf_ids; /* ID to subbuf VA */ > struct trace_buffer_meta *meta_page; > @@ -5224,6 +5225,9 @@ static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) > { > struct trace_buffer_meta *meta = cpu_buffer->meta_page; > > + if (!meta) > + return; > + > meta->reader.read = cpu_buffer->reader_page->read; > meta->reader.id = cpu_buffer->reader_page->id; > meta->reader.lost_events = cpu_buffer->lost_events; > @@ -6167,7 +6171,7 @@ rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu) > > mutex_lock(&cpu_buffer->mapping_lock); > > - if (!cpu_buffer->mapped) { > + if (!cpu_buffer->mapped || !cpu_buffer->meta_page) { > mutex_unlock(&cpu_buffer->mapping_lock); > return ERR_PTR(-ENODEV); > } > @@ -6194,7 +6198,7 @@ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer, > if (inc && cpu_buffer->mapped == UINT_MAX) > return -EBUSY; > > - if (WARN_ON(!inc && cpu_buffer->mapped == 0)) > + if (WARN_ON(!inc && cpu_buffer->mapped < cpu_buffer->user_mapped)) > return -EINVAL; > > mutex_lock(&cpu_buffer->buffer->mutex); > @@ -6328,7 +6332,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, > > mutex_lock(&cpu_buffer->mapping_lock); > > - if (cpu_buffer->mapped) { > + if (cpu_buffer->user_mapped) { > err = __rb_map_vma(cpu_buffer, vma); > if (!err) > err = __rb_inc_dec_mapped(cpu_buffer, true); > @@ -6359,12 +6363,15 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, > */ > raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); > rb_setup_ids_meta_page(cpu_buffer, subbuf_ids); > + > raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); > > err = __rb_map_vma(cpu_buffer, vma); > if (!err) { > raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); > - cpu_buffer->mapped = 1; > + /* This is the first time it is mapped externally */ > + cpu_buffer->mapped++; > + cpu_buffer->user_mapped = cpu_buffer->mapped; > raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); > } else { > kfree(cpu_buffer->subbuf_ids); > @@ -6392,10 +6399,10 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) > > mutex_lock(&cpu_buffer->mapping_lock); > > - if (!cpu_buffer->mapped) { > + if (!cpu_buffer->user_mapped) { > err = -ENODEV; > goto out; > - } else if (cpu_buffer->mapped > 1) { > + } else if (cpu_buffer->mapped > cpu_buffer->user_mapped) { > __rb_inc_dec_mapped(cpu_buffer, false); > goto out; > } > @@ -6403,7 +6410,10 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) > mutex_lock(&buffer->mutex); > raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); > > - cpu_buffer->mapped = 0; > + /* This is the last user space mapping */ > + if (!WARN_ON_ONCE(cpu_buffer->mapped != cpu_buffer->user_mapped)) > + cpu_buffer->mapped--; > + cpu_buffer->user_mapped = 0; > > raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); >
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 28853966aa9a..aa8eb878e0d4 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -491,6 +491,7 @@ struct ring_buffer_per_cpu { unsigned long pages_removed; unsigned int mapped; + unsigned int user_mapped; /* first user space mapping */ struct mutex mapping_lock; unsigned long *subbuf_ids; /* ID to subbuf VA */ struct trace_buffer_meta *meta_page; @@ -5224,6 +5225,9 @@ static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) { struct trace_buffer_meta *meta = cpu_buffer->meta_page; + if (!meta) + return; + meta->reader.read = cpu_buffer->reader_page->read; meta->reader.id = cpu_buffer->reader_page->id; meta->reader.lost_events = cpu_buffer->lost_events; @@ -6167,7 +6171,7 @@ rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu) mutex_lock(&cpu_buffer->mapping_lock); - if (!cpu_buffer->mapped) { + if (!cpu_buffer->mapped || !cpu_buffer->meta_page) { mutex_unlock(&cpu_buffer->mapping_lock); return ERR_PTR(-ENODEV); } @@ -6194,7 +6198,7 @@ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer, if (inc && cpu_buffer->mapped == UINT_MAX) return -EBUSY; - if (WARN_ON(!inc && cpu_buffer->mapped == 0)) + if (WARN_ON(!inc && cpu_buffer->mapped < cpu_buffer->user_mapped)) return -EINVAL; mutex_lock(&cpu_buffer->buffer->mutex); @@ -6328,7 +6332,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, mutex_lock(&cpu_buffer->mapping_lock); - if (cpu_buffer->mapped) { + if (cpu_buffer->user_mapped) { err = __rb_map_vma(cpu_buffer, vma); if (!err) err = __rb_inc_dec_mapped(cpu_buffer, true); @@ -6359,12 +6363,15 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_setup_ids_meta_page(cpu_buffer, subbuf_ids); + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); err = __rb_map_vma(cpu_buffer, vma); if (!err) { raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); - cpu_buffer->mapped = 1; + /* This is the first time it is mapped externally */ + cpu_buffer->mapped++; + cpu_buffer->user_mapped = cpu_buffer->mapped; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } else { kfree(cpu_buffer->subbuf_ids); @@ -6392,10 +6399,10 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) mutex_lock(&cpu_buffer->mapping_lock); - if (!cpu_buffer->mapped) { + if (!cpu_buffer->user_mapped) { err = -ENODEV; goto out; - } else if (cpu_buffer->mapped > 1) { + } else if (cpu_buffer->mapped > cpu_buffer->user_mapped) { __rb_inc_dec_mapped(cpu_buffer, false); goto out; } @@ -6403,7 +6410,10 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) mutex_lock(&buffer->mutex); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); - cpu_buffer->mapped = 0; + /* This is the last user space mapping */ + if (!WARN_ON_ONCE(cpu_buffer->mapped != cpu_buffer->user_mapped)) + cpu_buffer->mapped--; + cpu_buffer->user_mapped = 0; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);